Vagal nerve stimulation (VNS) systems and methods are disclosed in (for example) U.S. Pat. Nos. 7,778,703; 7,783,362; 8,401,604; 8,473,068; and 8,712,547, as well as U.S. published patent applications 2013/0184773 and 2014/0155949. See also Robert J. Henning et al. “Vagal nerve stimulation increases right ventricular contraction and relaxation and heart rate”, Cardiovascular Research 32, 1996, 846-853.